Electric contact plug



April 24, 1934.

C: E. GILBERT 'e2-IKK ELECTRIC CONTACT PLUG 'Filed Feb.A 5, 1932 INVENTOR f /v ATTORN v Patented Apr. 24, 1934 ELECTRIC CONTACT PLUG Charles E. Gilbert, New York, N. Y., assignor to Gilbert & Hertz, Inc., a corporation of New York Application February 5, 1932, Serial No. 591,006

5 Claims. (Cl. 173-332) My invention relates to electric plugs for making connection between electric wires and apparatus such, for example, as iiatirons, toasters and other devices equipped with contact prongs.

Heretofore, plugs of this general character have included a body in two pieces of such internal structure that when fitted together, the required recesses and channels for the contact members and wires are provided, the two halves being held together by one or two very small bolts. In use,

` it has been found impossible to keep the bolts tight and plugs of this construction are chronically out of order. Very frequently a nut drops oi the bolt, whereupon the plug falls apart with resulting short circuits, and if the nut is lost, as may easily happen in view of its small size, the plug is useless.

Furthermore, to assemble the contact elements and wires within the plug body is an extremely tricky and annoying task. Each contact element must be held in its shallow recess in one-half of the body and the wire attached to it must at the same time be fitted and retained in the tortuous channel provided for it, while the other half is being fitted on. In view of the fact that insulated wire has suflicient spring to resist bending to some extent, it is next to impossible to persuade the contact members and the wires to stay in place in the channels during assembly. In addition, the connection of the wires to the usual screw binding posts is rarely done in a secure and workmanlike manner by the average person and at any rate requires the use of tools.

My plug overcomes all of these objections. The body may be molded in a single piece. Each contact element may also be a single piece. The plug may be assembled with the greatest ease by anyone without the-use of tools or an understanding of mechanical or electrical matters. There are no bolts, binding screws or other parts which can become loose and yet the contact members and wires may be removed and replaced without difficulty. It is not even necessary to remove the insulation from the wires. In fact, it should not be removed since perfect electrical connection is obtained without removing it and its presence renders short-circuiting impossible even in the hands of the most careless and inexperienced person. In addition, my plug may be manufactured with great economy and hence appeals to manufacturer and user alike.

In the accompanying drawing I have selected a form of my plug for purposes of illustration, which is particularly suited for household use with an electric iiatiron. However, I do not intend vto limit my invention to this particular form or this particular use.- Obviously, it may be made in many other forms and for many other uses.

Of the drawing, Figure 1 is a general view in perspective of my plug completely assembled with the exception of the closing and retaining plate;

Fig. 2 is a cross section of the body of the plug along the line a-a of Figure l, and also showing one contact member in position with wire attached;

Fig. 3 is a View in perspective of one of the contact members;

Fig. 4 is a View in perspective of the plate which closes the open end of the plug and holds the contact members in position;

Fig. 5 is a plan view of this plate;

Fig. 6 is a fragmentary view of another form of contact element; and

Fig. 7 is a fragmentary view of the spiral cable guide.

My plug consists of a body 1 which may be molded complete in a single piece and by a single operation. This body is provided with a tubular central aperture 2 extending longitudinally entirely through the body and two recesses Sand 4, one on either side of and parallel to the central aperture, as shown in Fig. 2. The central aperture communicates with the side recesses for a portion of their length through slots 5 and 6 of suiiicient width to permit an insulated wire to pass therethrough.

The two side recesses are `for the reception of the contact elements whereby connection is made between the wires of the electric cable and the fiatiron or other electrical device. Each recess consists of a suitably shaped portion 7 for the reception of that part of the contact member designed to make contact with the prong on the atiron and a rectangular portion 8 which coincides in position and length with the wire gripping portion of the contact member. An extension 9 in the upper end of each recess provides space for the upper end of the contact member.

At the open end of the body the inner walls of the central aperture and side recesses are cut away as shown at 10 to provide an elongated, substantially rectangular space into which the ared free ends of the contact members may project. The extreme outer end of the body is also provided with a shoulder 11 against which a closing and retaining plate 12 seats. This retaining plate consists of a thin plate 12 of any suitable nonconducting material having a shape correspondsov ing to that of the open end of the body and provided with two apertures 13 and 14.

It is also provided with diagonal slots 15 and 16 and with outwardly projecting lugs 17 and 18. The slots permit retraction of the lugs so that the plate may be sprung into position against shoulder 11, whereupon the lugs will snap into openings 19 and 20 formed in the sides of the body. The body is also provided with exterior, longitudinal channels 21 terminating at the openings 19 and 20, which give access to the lugs from the exterior so that they may be pressed inwardly to disconnect them from the body, thus permitting removal of the plate whenever it is desired to take out the contact members. The apertures 13 and 14 should be of sucient size to readily admit the Contact.k prongs of the flatiron but smaller than the extreme end of the contact member so that it may act as a retainer for the contact member.

The upper end of central aperture 2 is threaded or provided with a threaded sleeve molded into the body, as shown at 22 for the receptionof a spiral wire cable guide 23, which is screwed into place. Heretofore, guides of this sort have been provided; with an enlarged iinal turn designed to t into an annular recess within the top of the body. With this arrangement, a relatively light pull is suicient to dislodge it. As stated above, the guide of my device is screwed into the body and cannot be pulled out. Furthermore, it cannot work loose or be accidentally unscrewed since I bend the extreme end back upon itself, as shown at 24. When the guide is screwed into the body this endfslides readily along the threads, but tends to resist motion in the opposite direction through the tendency of its end to dig into the threads. This tendency can be overcome without difficulty but it insures that the guide will not unscrew of its own accord.

The type of contact member which I have designed for use in this device is illustrated by Fig. 3. It consists of a single piece of conducting material which, in the form shown, may be stamped and bent into iinal shape by a simple manufacturing operation, thus providing a very inexpensive contact member and one which cannot possibly fall apart or loosen up since it is in a single piece without screws, rivets or other things of that na- ,with cylindrical contact prongs so that the cont'ct element which engages with them is ordinarily in the form of two longitudinal channels, as shown in Fig. 3, but as this is not always so I prefer the form shown in Fig. 6 in which one end 26 is stamped into the form shown and the other end 27 left at, since thereby a universal connection is provided for round, flat, square or otherwise shaped prongs. The end of each channel is preferably, slightly flared to act as a guide for the contact prong. Above the upper ends of the channel portions of the contact member is the wire gripping jaw 28 which consists of a at extension 29 on one side and an extension 30 on the other side of substantially the same length, but provided. with insulation piercing teeth 31 formed by serratingthe edges of this portion and bending them at right angles to their original plane.

Immediately above the flat portion 29, small lugs 32 are provided which act as a stop to prevent the insertion of the wire above the wire gripping jaw 28. The contact member should be made of some springy material so that when it is bent into the form shown in Fig. 3, its halves will normally springr apart somewhat to permit of ready insertion of the insulated wire and also so that in use it will maintain a positive wire gripping and prong gripping power no matter how many times it is disconnected.

The plug is assembled for use in the following mannen-The electric cable is rst inserted from the top through the central opening 2 until it projects beyond the bottom. The woven covering surrounding both wires is then slipped back to expose the ends of the individual insulated l wires within. A Wire with its insulation intact is then slipped between the two halves of a contact member until it is positioned transversely across the wire gripping jaw 28. The resilient character of the contact member will hold this wire temporarily in position while the other wire is similarly positioned in the other contact member. Then each contact member is pressed to gether by the ngers and pushed upwardly into its recess 3 or 4 until fully seated within the 1g@ recess. 'I'he dimensions of the rectangular section 8 'of each recess are such that when the contact member is fully seated, the wire gripping jaw 28 is forced together sufficiently to cause the teeth 31 to pierce the insulation of the Wire and 105 thereby establish electrical contact.

The diameter of the portion 7 of each recess is such that when the contact member is in position the prong gripping section thereof ts loosely therein` to permit this portion to be sprung apart somewhat by the insertion of the contact prong.

Means are also provided for relieving the contact jaws of strain in case the cable is suddenly jerked as frequently happens in use. This is accomplished simply by terminating the slots 5 and 6 between the recesses and the central opening at a point 33 slightly below the lower end of jaws 28. The wires when positioned in the contact members and the contact members inserted in the body first slip upwardly through the slots 5 and 6, nally coming to rest against the shoulders at the upper ends of the slots. 'I'hese shoulders being below the lower end of the jaws 28 cause the wires to bend sharply at that point. Any pull upon the cable will therefore be absorbed by the wires at these bends and will not be communicated to any appreciable degree to the jaws, thus insuring that the contacts will not be subjected to severe strain. In order to furnish suiiicient room for the wires to be bent in this way, each recess should, of course, be considerably wider than its contact member adjacent the jaws 28, as shown at 34. y

Assembly of my plug is completed by snapping plate 12 into place on the open end of the body, as already described, and threading the spiral cable guiding spiral 23 into the threaded end 22 of central aperture 2. `The extreme economy,

simplicity, convenience and'efgiciencyfpf the plug 140 of my invention is obvious.'

I claim: 1, A contact for utensil plugs consisting' of a U-shaped piece of metal with insulation piercing prongs intermediate the bend and ends of the U which will pierce the insulation of a wire when pressed together, the open ends of the U being adapted to receive a prong contact. I

2. An electric plug comprising a one-piece molded body provided with an internal recess open at one end, a contact element within said recess consisting of an elongated U-shaped metallic strip forming a prongreceiving contact adjacent its outer end, and having means adjacent its inner end for making electrical contact with an insulated wire through the insulation thereof.

3. An electric plug comprising a one-piece molded body provided with an internal recss consisting of an elongated U-shaped metallic strip forming a prong receiving contact adjacent its outer end, and also having means adjacent its inner end for making electrical contact with an insulated wire through the insulation thereof, said last mentioned means consisting of a jaw having insulation piercing teeth on one side and a stop on the other. l

5. An electric plug comprising a body having a central, longitudinal aperture passing through said body from end to end, a recess in said body laterally positioned with respect to said central aperture, said recess being separated from said central, longitudinal aperture for a portion of its length adjacent its closed end by a wall, said recess communicating with said central, longitudinal aperture throughout the remainder of its length through a slot, and a contact element positioned within said recess and provided with a prong contacting and also a wire gripping and insulation piercing portion.

' CHARLES E. GILBERT. 

